It is currently Wed Jun 28, 2017 10:16 am

All times are UTC - 7 hours



Forum rules


1. NO BLATANT PIRACY. This includes reproducing homebrew less than 10 years old, with the exception of free software.
2. No advertising your reproductions, with the exception of free software.
3. Be nice. See RFC 1855 if you aren't sure what this means.



Post new topic Reply to topic  [ 25 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: Thu Jul 07, 2016 6:33 am 
Offline

Joined: Tue Nov 23, 2004 9:35 pm
Posts: 588
As a kind of ultimate mod or challenge, I think it is quite possible today to make a NES version of the FDS RAM Adapter given the skills in the collective community. You need to put much of this inside a NES cartridge shell :

Image

The board will have to be custom designed and will probably take up 2/3rds of the cartridge shell, maybe more. However, if you do it the way I suggest that Nintendo would have done it, you can save a bit on the complexity.

First, you do not need to implement the expansion port shown in the top right of the above picture.

Second, the NES provides a system clock signal on pin 37, so you can save some space and routing there. This signal is not on the expansion connector and I believe Nintendo put it on the cartridge connector specifically for this purpose.

Third, you don't need the right-angle cartridge connector, saving space and complexity.

Fourth, you don't need to use a cable, you use the expansion pins. You have 10 pins and you need 9 signals : Audio Out, Serial In, Serial Out, $4025W.0, $4025W.1, $4025W.2, $4032R.0, $4032R.1, $4032R.2. You tie EXT7/BATT to ground to tell the adapter that battery power is always good.

Fifth, mixing happens inside the NES, so you can simplify the audio mixing circuit a bit.

The schematic for the FDS RAM Adapter is here : file:///D:/FC_HVC-FMR-01-04_05.pdf

The chief difficulty is desoldering that 64-pin RP2C33 and soldering it to a board without destroying the chip. There must be the customary space for the lockout chip. You will also need an ENIO board to route the signals from the RAM Adapter to either a disk drive or an FDSStick or similar. Take the +5v and GND from the expansion connector.

This design works for a front loader but not a top loader. For a top loader, you will need to route the cable signals to a cable, which requires a hole somewhere in the cartridge shell. You will probably need to swipe the crystal from the donor FDS RAM Adapter as well. Of course, given that you can use the FDS RAM Adapter with top loader and a 60-to-72 pin adapter and a resistor mod (vertical support strongly suggested), this would only have any real benefit for front loaders.

_________________
Nerdly Pleasures - My Vintage Video Game & Computing Blog


Top
 Profile  
 
PostPosted: Thu Jul 07, 2016 10:32 am 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5848
Location: Seattle
Great Hierophant wrote:
The board will have to be custom designed and will probably take up 2/3rds of the cartridge shell, maybe more.
Nah, it'll be roughly the same size as a TKROM board.

Quote:
Fifth, mixing happens inside the NES, so you can simplify the audio mixing circuit a bit.
Uh... mixing happens inside the expansion port. Whether you use an ENI/O or a permanently-attached resistor, or even put a real FDS drive on the expansion port...

Quote:
The schematic for the FDS RAM Adapter is here:
http://green.ap.teacup.com/junker/119.html

Quote:
The chief difficulty is desoldering that 64-pin RP2C33 and soldering it to a board without destroying the chip.
Even though it's DIP, hot-air rework stations are still up to the task. This really just comes down to having the right tools.


Top
 Profile  
 
PostPosted: Thu Jul 07, 2016 11:00 am 
Offline
User avatar

Joined: Sat Jul 12, 2014 3:04 pm
Posts: 848
Quote:
file:///D:/FC_HVC-FMR-01-04_05.pdf
Can't link local files like that, chummer.


Top
 Profile  
 
PostPosted: Sat Jul 16, 2016 3:29 pm 
Offline

Joined: Fri Jun 12, 2015 10:20 am
Posts: 21
I think it would just be easier to design a dongle that lets you connect the RAM component to the pin connector of the NES. Not to discourage the idea here, because it would be neat and I'd like one, but the fact it hinges on harvesting chips from an already working RAM adapter pretty much kills the likelihood of any large scale production.


Top
 Profile  
 
PostPosted: Sat Jul 16, 2016 6:29 pm 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5848
Location: Seattle
... You mean like this?

The right-angle connector in the FDS base, combined with the long NES cartridges and the door on the front-loader's enclosure, basically ruins any practical chance on using it on a front-loading NES without extensively modifying the NES itself.

As a result, you may as well re-engineer the whole thing at that point, it's really not that hard to get a solder pot or a hot-air rework station to move the 2C33 and two/five RAMs over.


Top
 Profile  
 
PostPosted: Mon Jul 25, 2016 3:59 pm 
Offline
User avatar

Joined: Sun May 27, 2012 8:43 pm
Posts: 1269
I had plans to make something like this, where I'd cut down or rebuild the FDS adapter to fit in an NES shell, wire up the cart slot, and fit one of Loopy's FDS boards in there too.


Top
 Profile  
 
PostPosted: Tue Jul 26, 2016 5:31 am 
Offline

Joined: Fri Jun 12, 2015 10:20 am
Posts: 21
Look up a 'Honey Bee Family Adapter'. It would be simpler to wire an extension from a 60 to 72 pin adapter for the same effect, basically.

I've been tempted to cut a ram adapter down into a NES cart too for myself, you can get yellow plastic shells, think how appropriate that would be to slap a pair of Diskun eyes on the face of it.


Top
 Profile  
 
PostPosted: Tue Oct 04, 2016 2:49 pm 
Offline
User avatar

Joined: Thu Oct 30, 2008 8:11 pm
Posts: 37
Location: Nashville, TN
I have been thinking about this also. And working toward a solution. I like the FDS a lot. I like Nintendo too, and electronics...

I've been learning Verilog for almost a year now. It is much fun. So I wanted to do something cool (in my opinion) with my new knowledge. Of course, first thing to mind is "better FPGA cartridge!"...yeah, we're working on that, but it's not so exciting (lacking innovation). I wanted to make a RAM Adapter for the NES. This project started as just an idea...I began checking on various things for the project; such as that cable used to connect to the disk drive, how to actually route the cable (expansion port is nice...), what types of "extras" can something like this have. Lots of positive feelings about the project at this point, so I pulled out my FPGA dev board and opened up ISE...

Some weeks later, I have a fully functioning (minus the sound) RP2C33 implementation. I have tons of ideas for the thing. Like disk emulation built-in, disk duplication features, NSF player...what else?

The BIOS is an issue, there will be an SD card slot on the cartridge. Used mainly for storing the disk images for the built-in disk emulation solution ("Magic Wild Card Pro"), but will also be the place where the user provides a disk system BIOS file.

Just for fun a made a video of the thing hooked up to my CopyFami, and I load some games with it.

https://youtu.be/ZzIYUHOwfPo


Top
 Profile  
 
PostPosted: Tue Oct 04, 2016 3:20 pm 
Online

Joined: Sun Sep 19, 2004 11:12 pm
Posts: 18535
Location: NE Indiana, USA (NTSC)
Has anyone documented all entry points into the FDS BIOS used by commercial games and which are timing-sensitive? The possibility that a game might jump into the middle of a routine is the big barrier to just pulling a Compaq.


Top
 Profile  
 
PostPosted: Tue Oct 04, 2016 3:28 pm 
Offline
User avatar

Joined: Thu Oct 30, 2008 8:11 pm
Posts: 37
Location: Nashville, TN
tepples wrote:
Has anyone documented all entry points into the FDS BIOS used by commercial games and which are timing-sensitive? The possibility that a game might jump into the middle of a routine is the big barrier to just pulling a Compaq.


The list on the wiki page https://wiki.nesdev.com/w/index.php/Family_Computer_Disk_System and the list in Brad Taylor's document are all that I've ever encountered messing with the FDS bios some years ago. I managed to get HLE bios stuff working for most of the games out there with my emulator nesemu2. You can see my HLE code which gets most games working. The issue that i stopped at was the bios call $EC22 which does some strange logic i never reversed, which prevents that strange mario brothers with the same image on the screen as that one rice seaweed packet flavoring things I used to get from my Japanese aunt as a kid. Wow, I really got off there.


Top
 Profile  
 
PostPosted: Tue Oct 04, 2016 6:57 pm 
Offline
User avatar

Joined: Sat Jul 12, 2014 3:04 pm
Posts: 848
Was going to ask what the pinout for the cable was, then checked the wiki, found it wasn't there, found that the schematic on http://green.ap.teacup.com/junker/119.html pointed at a text file back here with the parodius version of http://nesdev.com/FDS%20technical%20reference.txt whch DID have it, so I put it on the wiki


Top
 Profile  
 
PostPosted: Tue Oct 04, 2016 11:06 pm 
Offline

Joined: Tue Nov 23, 2004 9:35 pm
Posts: 588
deadbody wrote:
Some weeks later, I have a fully functioning (minus the sound) RP2C33 implementation. I have tons of ideas for the thing. Like disk emulation built-in, disk duplication features, NSF player...what else?
https://youtu.be/ZzIYUHOwfPo


All of those are good ideas, but an FDSStick does disk emulation and disk duplication. Ultimately what we need is an accurate PR2C33 hardware implementation. Loopy, krikzz and kevtris, in the NES Powerpak, Everdrive N8 and the Hi-Def NES all tried hard but their solutions are lacking.

_________________
Nerdly Pleasures - My Vintage Video Game & Computing Blog


Top
 Profile  
 
PostPosted: Wed Oct 05, 2016 12:46 am 
Offline
User avatar

Joined: Sat Jul 12, 2014 3:04 pm
Posts: 848
Do you have specifics, or is it simply the general "we need a delayered/RE'd RP2C33 and nobody's funded/done it yet"?

Hmm, no 2C33 pinout on the wiki, other than bits from an old doc. The schematic upthread on junker has one, though.

Though, it would seem like a Japanese enthusiast would get there first, if there's a corresponding central community, simply because they need not import to get the Famicom, FDS…


Top
 Profile  
 
PostPosted: Wed Oct 05, 2016 10:18 am 
Offline

Joined: Sun Apr 13, 2008 11:12 am
Posts: 5848
Location: Seattle
I'm pretty certain that the problem GreatHierophant referred to in the FDS is the sound simulation ... so deadbody having not touched that part yet just leaves a big question mark for now.

I'd arbitrarily assume that the "solution" is implementing the sound using only nsfplay as reference, and not the other subtly-wrong documents about how the FDS audio works.


Top
 Profile  
 
PostPosted: Wed Oct 05, 2016 10:38 am 
Offline

Joined: Tue Nov 23, 2004 9:35 pm
Posts: 588
Yes, I was referring specifically to FDS Audio and its modulation unit. No one has documented how it works in hardware and games like Bio Miracle Bokutte Upa require an exacting simulation or they will not sound correct. That game sounds wrong in all three devices I mentioned.

_________________
Nerdly Pleasures - My Vintage Video Game & Computing Blog


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 25 posts ]  Go to page 1, 2  Next

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 4 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group